Characteristics of electrode wear in resistance spot welding dual-phase steels

Hot galvanization dual-phase steel is a newly developed steel to be used in auto body to meet automobile light weight and safety requirement, which has high strength and good corrosion resistance. But welding of galvanization steels led to serious and uncertain electrode wear, which resulted in short electrode life and inconsistent weld quality. Experiment was carried out to study characteristics of electrode wear in welding 0.8 mm thickness galvanization dual-phase steels with 600 MPa strength (DP600) by servo weld gun. The characteristics of electrode radial wear and axial wear were compared with between DP600 and uncoated steels. The results showed that when welding DP600, more alloy products and electrode deformation were produced to make electrode diameter increase at earlier wear stage, which took higher electrode wear rate at this stage. Growth of pitting on electrode-tip face accelerated electrode invalidation. Undersized nugget was formed because of electrodes wearing out.